[Diapositivo]

I use the much maligned Combiplan with no leaks. I have say though, initially I did until I figured out the issue. You press the lid on thinking it is tight and secure, dribbles persisted. Because the lid is softer rubber it "grabs" a bit and doesn't really secure, water tight unless you apply a good deal of pressure all the way around. I do it by pressing the tank bottom to my chest, then working my fingers around the rim firmly press the lid against the rim of the tank. No leaks since and I do inversion agitation.

I do the same but I press the tank on a table and I press with my weight on it. I really press hard checking all the rim is well pressed. The "click" is not enough as experience shows.

That work but a thermic flask design would probably be better for inversion use. I use open tanks (Jobo with "lift") so I don't think I would have a substantial advantage in using such a design.

I would advice against trying with a thermic flask as developing produces gases and thermic flasks don't have a vent they could, who knows, "explode".